1. Field of the Invention
The invention generally relates to an exercise machine and, more particularly, to a progressive in-line resistance exercise machine.
2. Background Description
The strengthening of abdominal and lower back muscles as well as other muscle or muscle groups are important to one's posture and overall health. To strengthen one's abdominal muscles, several types of exercises and exercise machines are available and known. One type of exercise is a conventional sit-up. However, in a conventional sit-up there is a considerable amount of lower back stress and a lack of head and neck support throughout the sit-up motion.
By way of example, FIG. 1 is a highly schematic representation of a conventional sit-up. In this representation, (a) represents the fulcrum point (lower back of a user), (b) represents the user, (c) represents the applied load, (d) represents the force and (e) represents a motion by the user (b). As can be seen, the force component (d) and the load component (c) are perpendicular to one another. This results in a pressure at the fulcrum point (a), which adds undue stress to the user's back. Also, with the motion of the sit-up, at about 58% of the full range of motion, the user uses less concentric contraction force as they are isometric contraction; to support a bodyweight against gravity. Thus, the user is performing a very ineffective isometric contraction at this point. Additionally, during the motion of the sit-up, especially during the initial stages of the sit-up, the head, neck and lower back are not supported against the load, i.e., gravity, very effectively. This may result in injury or undue strain placed on the neck and lower back, in the least.
Exercise machines have been designed to overcome some of these shortcomings of a conventional sit-up. For example, weight machines have been devised to assist the user in strengthening the abdominal muscles and back muscles while supporting the head and neck. However, weight machines are not portable, and are typically very expensive to purchase. Additionally, these known weight machines, which use pulley systems, do not provide a full range of progressive resistance for the full range of motion of the exercise.
Other exercise machines are portable such as, for example, an abdominal roller machine. These machines require the user to lie on the floor during the exercise. These machines do not provide a progressive resistance during the full range of motion of the sit-up and actually restrict the beginning point of exercise and, some of the same stressful forces and loads as with the conventional sit-up are still applied to the user. Thus, these machines do not make the sit-up more effective than that of a conventional sit-up.
The invention is directed to overcoming one or more of the problems as set forth above.